1. Field
This invention relates to refrigeration monitoring systems, and more particularly to retail frozen food display case refrigeration monitoring systems.
2. State of the Art
Food distribution systems today include frozen food items which are made available at the retail distribution level in retail frozen food cases or counters. A typical frozen food case is an elongated counter with a refrigeration system which supplies a blanket of very cold air to maintain the frozen food items positioned or placed therein in a frozen condition while permitting customers reach-in access to the food items. Failure of the refrigeration system supplying the cold air to the refrigerated case is a known occurrence and one which occurs perhaps all too frequently. Various alarm circuits have been suggested to alert personnel of the existence of a failure in the refrigeration system to preclude losses by the thawing of the frozen food placed in the case.
U.S. Pat. No. 4,028,688 (Goleman) suggests an alarm system which supplies an alarm signal when the frozen food case air temperature reaches a preset point. The alarm signal is transmitted to a receiver which immediately causes an external phone dialer to dial an external phone number. U.S. Pat. No. 3,707,851 (Mcashan Jr.) discloses a refrigeration efficiency monitoring system. U.S. Pat. No. 3,594,749 discloses a system for monitoring the refrigeration system of display cases using what appears to be thermal-bulb gas connections to macro-switches. U.S. Pat. No. 3,234,749 (Quick) discloses a refrigeration system having therein an alarm system to alert the operator of malfunctions. U.S. Pat. No. 3,415,070 (Weum) also discloses a refrigeration warning system.
The refrigeration alarm systems heretofore known frequently rely upon extensive wiring or piping connections to transmit alarm signals or other data related thereto. In today's supermarkets or similar retail food outlet facilities, wiring or piping may be unacceptable. Further, the cost of installing extensive wiring and piping may be quite prohibitive. In addition, the systems heretofore known, including specifically the system of Goleman, do not provide for the integration of an alarm signal or a time delay to preclude spurious or random alarms. The existence of random or spurious alarms is quite undesirable in that it conditions monitoring personnel to not take immediate corrective action upon the existence or occurrence of an alarm. The food losses related to the failure of refrigeration systems at the same time is quite high and can exceed several thousand dollars per year for a typical supermarket having one or more frozen food cases or counters. An improved alarm system not requiring wiring or piping and further providing for the integration of a signal and also for an operational check from time to time of the detector system itself is desirable.